There exist head-mounted displays (HMDs) to be mounted on the head of a user for visual appreciation, as described in PTLs 1 to 3, for example. Some of the HMDs are equipped with a camera that captures an image of what is ahead of a display section of the HMD so that the user will recognize what is taking place before the display section using the captured image being displayed.
There also exists a technology for visual line tracking allowing the direction of the user's visual line to be tracked using iris detection.